1. Field of the Invention
The present invention relates to power supply arrangements for use in distributed entertainment systems.
A distributed entertainment system typically comprises audio/visual source equipment, such as a CD player, DVD, VCR, and the like, which is located in one room and linked to several zones, e.g., rooms, in the home. Such a system often includes a hub, which is situated near the audio/visual source equipment and which links the audio/visual source equipment to apparatus located in the various zones. The zone apparatus may, for example, include an amplifier and may also include means for control of certain characteristics of the output of a selected component of the audio/visual source equipment, e.g., volume or sound characteristics such as bass or treble, etc. The zone apparatus may also include means for exerting control over the source equipment itself, e.g., track skip, access of a certain preset/channel, etc.
2. State of the Art
In a distributed entertainment system, electrical power is usually conveyed from a main power supply in the hub by means of a respective pair of power supply conductors to each zone apparatus. Audio signals are transmitted from signal processing circuitry in the hub to each zone apparatus, for example, by means of the power supply conductors or by means of a separate pair of signal conductors. Control and data signals, which are often in a digital format, for example, signals for controlling the source equipment output characteristics, can also be transmitted to and from the signal processing circuitry to each zone apparatus by similar means.
Typically, the signal processing circuitry, the zone apparatus and the power supply each utilise power supply rails, from which power is drawn. Often, the power supply rails comprise multiple rails, of which one is a reference power supply rail.
During operation, the natural electrical impedance of the power supply conductors between the main power supply in the hub and the zone apparatus will cause the voltage at the power supply rails of the zone apparatus circuitry to be different than that at the hub. This is of particular concern in distributed entertainment systems where the cable runs can be substantially longer than in normal domestic entertainment systems.
The aforementioned problem can be exacerbated in distributed entertainment systems that include an amplifier module in the zone apparatus, which is powered from the hub via the power supply conductors. The electrical current requirements of zone amplifier apparatus can be substantial, thereby causing a large potential drop across a distributed impedance of the power supply conductors, which in turn changes a level of the power supply voltage that is delivered to the zone apparatus.
In addition, the electrical current requirements of a zone apparatus, which includes, for example, an audio amplifier, cannot only be significant but can also vary to a large extent. Thus, there can be a large variation in the level of the power supply voltage that is delivered to the zone apparatus. For instance, the current drawn by an amplifier usually varies considerably in sympathy with the variation in the amplitude of the output music signal over time.
The change in level of power supply voltage at the zone apparatus can cause corruption of the wanted audio, data and control signals that are transmitted to and from the zone apparatus.
For example, in the case of transmission of control and data signals from the hub signal processing circuitry to the zone apparatus, a voltage level mismatch can arise between the signal processing circuitry and the circuitry in the zone apparatus that receives the control and data signals. More specifically, a mismatch of the high and low logic levels of the digital circuitry in the signal processing circuitry and the zone apparatus can arise. The mismatch can cause a failure in recognition by the zone apparatus of control and data signals sent from the signal processing circuitry.